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How Does Machine Espresso Work?

Machine decent espresso machine makes use of precise pressure and amazing filter technology to make the delicious coffee we enjoy. How exactly does it work?

To make an espresso hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee however the main difference lies in the pressure.

The Head of the Group

The group head is the portafilter that you insert when brewing espresso. It disperses the water into the portafilter, and then controls the pressure of the extraction. There are numerous kinds of group heads each with its own advantages and disadvantages. Some focus on temperature stability, some on pre-infusion options, and others are designed to control the lever. Some are a combination, like the E61. This is a popular choice among baristas as it provides a variety of advantages in one package.

As you can see in the above photo the group head has a number of notches. It is possible to place your portafilter in these notches and then twist the head to lock it. A rubber gasket is located within the notches to make a seal when you insert your portafilter. The notches on the head allow for a precise position of the portafilter which is vital to ensure an even extraction.

The group head not only allows the portafilter to be inserted easily however it also keeps a constant temperature. This is done by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is always at the right level to extract the coffee. It is important to realize that even a few degree difference can make the difference between a good and great espresso.

The Pump

Unlike manual piston machines, that use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure necessary for espresso extraction. The pressure builds up by drawing tap water from a reservoir and pumping it through a heat exchanger prior being pushed through the ground coffee in the group head.

Pumps are generally less expensive and last longer than piston-driven machines. However, both kinds of machines are susceptible to degrading due to excessive use and insufficient cleaning. Pumps are also more complicated mechanically, which could increase the price of even the most basic models.

Certain espresso machines utilize steam pressure instead of a pump to make espresso. The disadvantage of this is that the same boiler that produces steam also raises the temperature of water to boiling which can cause over-extraction. They also have to continually rebuild their pressure between cups. This requires energy and time.

Many espresso machines make use of either a rotary or vibration pump, which has a vibration model using a vibrating disc to generate the pressure, and rotating models that push hot water through the grounds at high speed. Both types of machines can produce an excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler makes the water warm to the perfect temperature for extraction. The steam that is produced reaches the portafilter containing the ground espresso and gets funnelled down into the cup. During this process, steam causes pressure to push through the coffee grounds. This results in a layer crema that is then poured over. This is the hallmark of a good espresso.

There are three types of espresso makers, and they differ in the type of pump they employ and how hot the brew is. There are many ways to control the brew and the size of the cup that can be produced by the machine.

The first espresso coffee machine home machines were steam-type. They utilized one boiler to create both steam and brew, however, the pressure they could produce was very low - just two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. This is the reason why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso maker barista machine.

The most common espresso machine is a semiautomatic with an electric pump. This is what people envision when they think of an espresso machine. With a semi-automatic espresso machine, you must grind the beans and tamp them yourself but the pump controls the flow of water and pressure. This is a great combination of human control and mechanised reliability.

The Filter

Typically, espresso machines employ filters that separate the grounds of coffee machines espresso when they pass through the hot water. The filter is also a crucial element of the temperature control system because it stops the machine from overheating.

It also aids in flavor, since a filter can allow for a longer bloom phase. This allows the beans to release their flavor and gives the chance for better extraction.

However, it is important to remember that even a high-quality filter could result in a bad cup of coffee, since the quality of the beans and extraction is crucial.

It's here that the magic occurs. This is what makes buy espresso machines taste so delicious. The grouphead (also known as the brewhead) is where you place the portafilter, the device used to place the coffee grounds in, when making espresso.

In a steam-driven espresso machine, hot water is heated in an airtight container to create steam, which is then pushed through the grounds at high pressure. These machines are cheaper and easier to maintain than pumps-driven models. They are however limited for creating the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

In recent times, espresso machines powered by compressed air-pump are becoming increasingly popular. They utilize an air compressor to push hot water across the ground, and are more mobile than electric steam-driven espresso machines.